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diff --git a/src/tools/clippy/src/docs/only_used_in_recursion.txt b/src/tools/clippy/src/docs/only_used_in_recursion.txt
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+### What it does
+Checks for arguments that are only used in recursion with no side-effects.
+
+### Why is this bad?
+It could contain a useless calculation and can make function simpler.
+
+The arguments can be involved in calculations and assignments but as long as
+the calculations have no side-effects (function calls or mutating dereference)
+and the assigned variables are also only in recursion, it is useless.
+
+### Known problems
+Too many code paths in the linting code are currently untested and prone to produce false
+positives or are prone to have performance implications.
+
+In some cases, this would not catch all useless arguments.
+
+```
+fn foo(a: usize, b: usize) -> usize {
+    let f = |x| x + 1;
+
+    if a == 0 {
+        1
+    } else {
+        foo(a - 1, f(b))
+    }
+}
+```
+
+For example, the argument `b` is only used in recursion, but the lint would not catch it.
+
+List of some examples that can not be caught:
+- binary operation of non-primitive types
+- closure usage
+- some `break` relative operations
+- struct pattern binding
+
+Also, when you recurse the function name with path segments, it is not possible to detect.
+
+### Example
+```
+fn f(a: usize, b: usize) -> usize {
+    if a == 0 {
+        1
+    } else {
+        f(a - 1, b + 1)
+    }
+}
+```
+Use instead:
+```
+fn f(a: usize) -> usize {
+    if a == 0 {
+        1
+    } else {
+        f(a - 1)
+    }
+}
+```
+\ No newline at end of file